The use of musculoskeletal allograft tissue in reconstructive orthopedic procedures and other medical procedures has markedly increased over the last decade. Over the past decade, more than five million musculoskeletal allografts have been safely transplanted. The most common allograft is bone. However, tendons, skin, heart valves and corneas are other common types of tissue allografts.
Prior to use, the allograft tissue must be evaluated for microbial contamination. The allograft product must be tested for bacterial contamination prior to release of the tissue for transplantation. Swabs are widely used in the pharmaceutical and medical device industry for evaluating microbial contaminants on small, hard, non-porous manufacturing equipment, in addition to detecting microbial contaminants in environmental monitoring programs. In the clinical setting, swabs are primarily used to diagnose clinical diseases. The use of swabs was adopted by the tissue banking industry several years ago for detecting microbial contamination. Swabs are used on porous, freeze-dried and frozen allograft products. It is not an uncommon perception that swabs are not all that sensitive or reproducible when detecting microbial contamination from various surfaces. The ability of the swab to recover contaminant microorganisms is dependent on two events; the first is its ability to “pick-up” viable contaminants from the surface of the article being swabbed and the second event, is the “release” of any microbial contaminants from the swab into an appropriate growth environment (e.g. solid agar medium or broth). In addition, on some allografts, the swab is not capable of contacting the entire surface area of the allograft. Moreover, some areas of the allograft are simply inaccessible to a swab, thereby not allowing for complete analysis of the allograft for microbial contaminants.
Another method used for detecting microbial contamination on allografts is destructive testing. Destructive testing using companion tissues (small sections of typically lower quality or unusable portions of the allograft) is routinely used to assess microbial contamination on entire allograft lots. This practice has come under intense scrutiny by regulatory agencies since the companion tissue may not be representative of the microbial contamination on entire allograft lot. Furthermore, the geometry of the companion tissue does not adequately represent the geometry of the entire allograft lot.
Recently, non-allograft materials from varying sources (bovine, ceramic, synthetic, etc.) have been used as a representative model of what the allograft tissue products are exposed to during handling and processing. The limitation with these materials is that they are not truly representative of the actual allograft. Furthermore, it is extremely difficult to fabricate synthetic samples to model every product category currently utilized for transplantation.
In the past, ultrasound has been utilized to minimize and/or eliminate microbial contamination of allograft products. Ultrasound is microbiostatic to most microbes, and is used primarily to reduce microbial loads from inanimate objects with specific bacteriocidal activity on gram-negative bacteria.
With the increased use of allograft products, there is a need to provide methods with improved detection of microbial contamination of allograft products.